Treatment of crude pyroligneous acid



March 1, 1932. E, A CH RLE 1,847,597

TREATMENT OF CRUDE PYROLIGNEOUS ACID Filed April 21, 1927 T Wain mi ting column oily layerdc g ante r Qlumm Va our;

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7 VGPOUTS Vapour hQduggt cucur L concq'nhahd qua avdischm-r Crude pxr'ofigna ous' gid Patented Mar. 1, 1932 UNITED STATES PATENT OFFICE.

ERNEST ANDRE CHARLES, F CLAMECYQFRLNCE, ASSIGNOR TO LA SOCIETE ANONYME DES PRODUITS CHIMIQUES DE CLAMECY (NIEVLRE), OF CLAMECY (NIE'VBE), FRANCE TREATMENT OF CRUDE P YBOLIGNEOUS ACID Application filed April 81, 1827, Serial No. 185,628, and in France. April 22, 1926.

' The liquid product resulting from the distillation of wood in a closed vessel comprises four main constitutents which are: neutral products, acid products, tarry products and water. This liquid is called crude pyroligneous acid;

The standard treatment of crude pyroligneous acid is based on the following principle: the acid, after having been more or less 10 rid of gum by any mechanical means, is

carbonate of soda,

heated in a still, unlessdirectly treated on issuing from the tar remover; in any and all cases, the vapors are passed through an alkaline lye (milk of lime, aqueous solution of etc.) wherein all the acid products (acetic acid and its homologues) are fixed, while the neutral products (methyl acetate, acetone, methyl alcohol, allyl alcohol, various oils, etc.) are condensed in a cooler located next to the apparatus containing the 30 tate;

3. Residual tar, more or less acid. The phlegms or magmas are discontinuously or continuously concentrated for the purose of obtaining the various grades of methyl 85 alcohol,-and it is observed that the more impurities the phlegms contain, the more difficult it becomes to obtain a high proportion "of wood or methyl alcohol relative to the total wood alcohol.

The metallichcetate solution has to be concentrated by evaporation and, in the case of has to be dried at a an amorphous-acetate, suitable temperature. The acetate obtained is ultimatel decomposed by a mineral acid it the manu acture of concentrated acetic acid is contemplated.

The object of this invention is to provide a process that will permit, through simple distillation in the presence of various bodies,

the separation of:

1. Phlegms containing acetoneand methyl acetate besides methyl alcohol;

2. Pyrogenated impurities containing, especially, allyl alcohol.

3. Acetic acid and homologues thereof, highly concentrated. i

It is well known that certain substances, such as benzene, have the property of forming, with methyl alcohol, a binar product having a minimum boiling point, w ich property is utilized in the present process to separate the meth 1 alcohol from its impurities; such product ing a mixture which yields methyl alcohol benzene, aliphatic hydrocarbons, chlorureted or uot,.certain light pe troleum fractionsIand carbon bisulfide. the case of benzene, for example, the mixture or product will boil at about 58 C. and contains in weight about 39% of methyl alcohol. Starting from the above observation, the process may be carried out in the following manner:

In abattery of stills A see the sin 1c figare of the accompanying rawing), t e pyroligneous acid is heated. The vapors evolved comprising a mixture having substantially the following composition:

Methyl alcohol 20% approximately Methyl acetate 4% approximately Acetone 2% approximately Acetic ac1d 5% approximately 011 2% approximately Water 67% approximately pass through piping 1 into acolumn B where they meet benzene led in through pipe 2 from decanter E. The object of adding the benzine in the column B is to carry away the productsfwhich have boiling points beyond a certain temperature, such as the'oils, the acetic acid and the water. The vapors from' the bina mixture thus formed are delivered to a coo er C through pipe 3, the condensed distillate from cooler being discharged into a small column I) where it meets water supplied by pipe 4. The heterogeneous mixture resultingfrom this treatment is decanted at E, the benzene returning through pipe 2 to column B and the methyl alcohol phlegms discharging at 5. The water supplied by pipe 4 is so adjusted the stills A reaches 69 (1., after which the benzene starts to distill oil. The benzene which returns to the column B is mixed at the head of the column with methyl alcohol,

methyl acetate and acetone. tity of vapors which are emitted by A and which contain large amounts of water prevent the benzene from descending to the bottom of the column B and consequently into A. The first part of the treatment, that is to say removal of alcohol, is completed. The pipes l are then closed and the'pipes 6 opened, and distillation is recommeuced.

The vapors then coming from stills A are led through the piping 6 into column F whence they are led into cooler G through pipe 7; the condensed distillate ultimately passing into a small column H and then collecting in decanter I. hen the vapors are at 98' ]O() C., substantially nothing but more or less acid water passes, while most of the pyrogeuated impurities (i. e., the wood oils, the most volatile and most readily distilled, are carried away at between 70 and 97 C. There is found in the decanter I a product constituted by two layers; a light oily layer and an aqueous layer having a low acetic acid content as compared with-that of the 'iyroligneous acid under treatment.

lvloreover, it the impurities (the oily layer)- are washed with water supplied by pipe 8, certain constituents, and especially allyl alcohol, pass into solution.

It is upon these observations that I base the second and the third parts of my process, since it will be readily understood that it the pyrogenated impurities carry away the water without carrying away appreciable quantities of acid, such impurities will only the first impurities by decantation at I.

In order that the acetic acid obtained may be rid of tar, it is suflicient to cause the concentrated acid to be led to a still J through The great quan pipe 11. From this still the acid is either extracted as it stands, or it is rectified by leading the vapors into a column suitable for obtaining the desired grade. Finally, the exhausted tar is drained from the stills A.

The process can be rendered continuous if care is taken to connect, as indicated by the figure, columns B and F to a group of stills analogous to A in staggered order.

By using any of the known methods the heat produced in the course ofthe various operations can be utilized to its fullest extent.

I claim as my invention 2-- 1. In a process of treating pyroligneous acid, the steps of distilling the crude pyroligneous acid; and adding benzene to the more volatile vapors resulting from the distillation the resulting product containing methyl alcohol, methyl acetate and acetone and hav ing a minimum boiling point. '2. In a process of treating pyroligneous acid, the steps-of heating crude pyroligneous acid; mixing the initialvaporstherefromwith benzene; cooling thebina-ry mixture thereby formed; adding water to the cooled product; decantin the resultant mixture; and mixing with free acid vapors the benzene recovered by the decanting.

3. In a process of treating pyroligneous acid, the steps of heating crude pyroligneous acid; mixing the initial vapors therefrom with benzene condensing the vapors; adding water to the condensate to form a heterogeneous mixture containin methyl alcohol phlegins and benzene; ecanting the lastnamcd mixture; and mixing withfresh acid yapors the benzene recovered by the decantmg.

4. In a process of treating pyroligneous acid, the steps of distilling crude pyroligneous acid until all the methyl alcohol contained therein has been driven off; heating the residue from the distillation; cooling the vapors from the distillation of the acid and thereby obtaining a condensate and water; decanting the condensate; and draining off the water.

5. Aprocess according to claim 4, in which tliecooled condensate is mixed with water prior to being decanted.

- In testimony whereof I afiix my signature.

ERNEST ANDRE GHARLES. 

